Illuminating device



Patented Mar. 25, 1941 UNITEDA 4s'rli'nzs PATENT osi-ica n $336,420' ILLUmNA'rlNG DEVICE Application February 9, 1939, Serial No. 255,528

, In the Netherlands February 21, 1938 7 claims. (c1. zut-4:4)l

Our invention relates lto a device for illuminating as intenselyV and as uniformly aspossible a plane surface',whose two dimensions do not exceed the ratio pf 1 to 10.` V

The devicela'ccording to the invention may be utilized for various purposes, but generally where a very strong illumination of a plane is desirable. Y

For example, the invention may be utilized for illuminating the nlm Agate of a projector, and in search-lights which are toilluminate a denlte objectJor example an airplane, with as great an intensity as possible.

' v own optical system, forexample with -a mirror.y

It has been proposed to illuminate a plane surface by the light emitted from a. plurality or separated punctiform light sources in which v case the illumination cones of the points of the illuminated plane: surface consist of a number ofy each containing twolight sources, three rows each containing three light sources etc. In other words it is generally necessary to use n light sources and to provide each light source with its The beams oizlight from the 11,2 light sources form f togetherv the'illurnination` cones-for the points of the plane suria'ceto be illuminated, and therefore each illumination cone is constituted by n? par-v -tial illumination 'conesf Y e In otherrknown devices, the arrangement is such that each of the light sources shines only on a portion of the surface to be illuminated with the result that the total illumination of that surface is eiected `by a plurality of light patches located next to and above each other. This has the drawback that .when one of the light sources l is extinguished, for example due to its becoming defective, the surface 'to be illuminated locally exhibits a dark spot.` Furthermore, lin such cases' it--is'not'feaslble to use. light sources of different types in order to correct the color of the ligljit.Y

The object of the present invention is to overcome the above disadvantages and for this purpose we use a limited number ot-linear light sources which are arranged parallel to each other. v Each of these light sources is provided with two optical cylindrical means which are separated in the immediate vicinity of the plane surlace tobe illuminated and that each of these light patches will at least substantially cover the surface with light. The light sources together with their optical means areso arranged relatively to one another that the illumination conesjof the points of the plane consists of a number of plane cones of light, each of which originates from one of the light sources.

In comparison with the prior device, it is nec- Y essary, whenV illuminating a given surface, for example a square surface, with a device according to the invention to useonly two, three, four, etc., lightsources arranged in parallel with each other. Thus, generally it is necessaryto use-only n lightsources which illuminate lia-thedesired nanner the plane to be illuminated with the aid of the aforementioned optical means. cooperating with the light sources. If the plane to be i1- luminated is of'rectangular section,only one row oflight sources arranged in parallel relationship with one another will be generally required. The illumination cones of the points of the plane thus consist of n partial plane conesI and the shape of the plane to be illuminated need not correspond with the shape of the light sources, but is dependent on the magniilcations of the cylindrical optical elements.

' Due to theirspatially-separated arrangement,

the optical cylindrical means co-operatingwth the light sources strongly restrict the astigmatism which would otherwise occur with the use of cylindrical elements. These mea-ns may be of different lrinds;v for example, we may use with each light source two cylindrical lenses, two cylindrical mirrors, or one cylindrical lens and one cylindrical mirror. Each` cylindrical optical element may-comprise in known manner several parts which are arranged in the immediate proximity of each other and may be cemented to one another. Owing to the action of thecylindrlcaly means theillumination cones of the polntsoi. the

plane are constituted by a number of plane ycones of light; This means that. each of the partial illuminationcones which consequently originate fromfonegsourceiof-.lightvexhibits n cross-section.A

fcaused by the `a slightly flattened shape' whic g elongated shape of' part' oi the optical elements utilized;

In one advantageous embodiment of the vdevice according to the invention the illumination cones of the points of` the plane consist of a number of plane cones of light practically adjoining each other.

When the plane to be illuminated as intensely as possible is formed by the film gate of a film projection apparatus it is desirable for a most economical use of the light radiated by the light sources to so choose the illumination cones of the points of the lm gate that they Will be located within the receiving angle of the projection lens arranged behind the film gate.

In order that the invention may be clearly understood and readily carried into effect, we shall describe the same in more detail with reference to the accompanying drawing in which:

Figure l is a sectionized view of a device according to the invention,

Fig. 2 is a section along line 2-2 of Figure 1,

Fig. 3 is a section along line 3-3 of Figures 1 and 2,

Fig. 4 is a sectional view of a device according" to another embodiment of the invention, and

Fig. 5 is a section' along line 5-5 of Figure 4.

The device illustrated in Figures 1 and 2 is used to illuminate a film gate l having a length b and a width a which are of a similar order of magnitude and in a ratio considerable less than 10 to 1. The device comprises two linear light sources 2 and 3 arranged parallel to each other and perpendicular to the plane of the drawing in Figure 1. The light emitted by light source 2 passes through a cylindrical lens 4 whose axis extends perpendicular to the plane of Figure l and through a second cylindrical lens 5 whose axis is parallel to the plane of Figure 1 and perpendicular to the axis of lens 4. In a similar manner the light emitted by light source 3 passes through cylindrical lenses 6 and 'I which are similar to lenses 4 and 5 respectively and similarly arranged with respect to each other and to the light source 3.

The light sources 2 and 3 may be high-pressure mercury-vapor discharge tubes of the type described in the U. S. Patent #2,094,694 to Bol et al., but other linear light sources such as an incandescent lamp with a linear filament may be used.v Furthermore, additional light sources together with lenses may be used. It should be noted that only two light sources arranged in parallel are used, and not a number of rows each containing several light sources as would -be the case if punctiform light sources were used.

The light emitted from the light sources i! and 3 is Vprojected to form luminous patches on the film gate I, and because of the separate arrangement the astigmatism is kept within tolerabl limits.

Due to the action of the cylindrical lenses 4 and 6 the light sources 2 and 3 are enlarged in their cross section (see Fig. 1) so as to illuminate the height a of the lm gate. In the section of Fig. 1, the cylindrical lenses 5 and 'I have substantially no effect upon the course of the light rays, but act merely as plano-parallel glass plates. When considering a point P at the film gate I, it appears that this point is illuminated by an illumination cone which, in the section in Fig. 1, consists of two partially-flattened illumination cones which originate from the light sources 2 and 3 respectively and have equal apical angles p defined by the light rays Z-A-P and Z-B-P, and q defined by light rays 3-C-P 'and B-D-P. The total apical anglejn this section of the cone of light at the point P is therefore p-l-q. and since the magnitude of this angle is also decisive for the brightness at this point itwvill be appreciated that the brightness under these circumstances, l. e. when both the light source 2 and the light' source 3 are4 radiating light, becomes as great as possible.

Behind the film gate l is arranged a projection lens 8 of a film projection apparatus. and as shown in Figures 1 and 2 the receiving angle of this lens has a value r. The illumination cone of each of thel points of the lm gate has an apical angle equal to P-i-q, which is substantially equal to the receiving angle r of the projection lens. It is obvious that if the receiving angle r of the projection lens is materially greater than the sum of the angles zH-q, there is no objection -to adding a third light source to the light sources 2 and 3.

When considering light rays 20 and 2l passing through the extreme parts of the light sources and also through the optical center of the cylindrical lens 4, it is seen that, as previously mentioned, the thickness d of each of the light sources is in creased in-such manner that each of the light sources is extended over the entire width a of the film gate. when one of the light sources is extinguished, the entire film gate I will remain illuminated, 'only the illumination cone of the point P in this case acquiring a lower value, viz.a value p. As a result the film gate I will be illuminated only with half of the maximum brightness.`

In the section of Figure 2,v the light source 3 exhibits 'a suflicient dimension so that the light source in this direction need be only slightly enlarged to illuminate the lengtlib of the'lm gate. Since the necessary enlargement in this direction is only small, the apical angle S of the illumination cone will in this section generally exhibit a value which is sufficiently high. Because of this it is unnecessary to arrange a plurality of light sources above one another. The apical angle S is defined by the light rays emitted from a point of the light source, for example the center O, and passing through the extreme points E and F of the cylindrical lens I which is operative in this section, and also through the point P. Furthermore, from Figure 2 and mainly from the course of the light rays emerging from the extreme points G and H of the light source 3 and passing through the optical center J of the lens 1, it appears that the length of the light source is such as to ll the dimension b of the film gate completely with light in this direction. In this sec tion the lens 6 serves as a plano-parallel plate and consequently does not affect the course of the light rays to any appreciable amount. The angle S is adapted to the receiving angle 4 of the projection lens 8.

Fig. 3 shows the position of the sections in the plane III- III of Figs. 1 and 2 of the two partial illumination cones having apical angles p and q respectively and distinctly shows the flattened shape of these cones, the width and length of the sections being indicated by the angles of Figs. 1 and 2. i

The device illustrated in Figs. 4 and 5 is intended for search-light installation, and comprises three linear light sources 9, I0 and I I, which are similar to light-sources 2 and 3, arranged parallel to each other and perpendicular to the plane of the 'drawingin' Figure 4.' In this case each light source is provided with a cylindrical mirror and a cylindrical lens. More particularly, a. cylindrical mirror I2 is arranged at the rear of light source 9 with its axis parallel thereto, and a cylindrical lens I5 is arranged in front of this light source with its axis perpendicular to the .axis of the mirror I2. In a similar manner a mirror I3 and lens I6 are arranged with light source It also appears from this that :n rangement, the transverse dimension of each of the light sources is extended by the action of mirrors l2, i3 and I4 so that they all exhibit the dimension c at the point of projection in R. The length of each of the light sources (see Fig. 5) is f3 such that the height dimension d of the object to be illuminated is completely filled with light byj" the action of the cylindrical lenses I5, I6 and I1."

While we have described our 'invention with reference to specic examples and applications,

o we do not wish to be limited thereto, but desire the appended claims to be construed as broadly as is permissible-in view'of the prior art.

What we claim is: l l

1. A device for intensely illuminating a plane whose dimensions are in a ratio less than 10 to 1,

comprising a plurality of linear light sources arranged parallel to each other in a row substantially transversely of the projection axis, means associated with each light source to enlarge the projected light and form light spots partly overlapping in `the vicinity of the plane and each covering substantially the entire plane with light, said means comprising for each light source two cylindrical optical members arranged in the path of the light emitted from the source and spaced apart with their axes perpendicular to each other and with one vaxis parallel to the longitudinal axis of the light source, the illumination cones of the points of the plane consisting of a plurality of o plane light cones each originating from one of the\light sources. i

2. A device for intensely illuminating a plane Whose dimensions are in a ratio less than 10 to 1, comprising a plurality of linear light sources arranged parallel to each other in a row substanfi tially transversely of the projection axis, means associated with each light source to enlarge the projected light and form. light spots partly overlapping in the vicinity of the plane and each covering substantially the entire plane with light, said means comprising for each light source two cylindrical optical members arranged in the pathr of the light emitted from the source and spaced apart with their axes perpendicular to each other and with one axis parallel to the longitudinal axis of the light source, the illumination cones of the points of the plane consisting of a plurality of adjacent light cones each originating from one of the light sources; A

n0 3. Aldevice for intensely illuminating a plane whose dimensions are in a ratio less than 10 to 1, comprising a plurality of linear light sources consisting of high-pressure mercury-vapor discharge tubes arranged parallel to each other in a row extending substantially transversely of the projection axis, means associated with each dislight source, the illumination cones of the points of the plane consisting of a. plurality of adjacent light cones each originating from one of the iight sources.

4. A device for intensely illuminating the illm 5 gate of a projection system having a projection lens arranged behind the fllm gate, comprising a plurality of linear light sources arranged parallel to each other in a row substantially transversely of the projection axis, means associated with each l0 light source to enlarge the projected light and form light spots partly overlapping in the vicinity of the film gate and each covering substantially the'entire area of the film gate with light, said means comprising for each light source two cy- 15 lindrical optical members arranged in the path of the light emitted from the source and spaced apart with their axes perpendicular to each other and with` one axis parallel to the longitudinal axis of the light source, the illumination cones 2o of the points of the ilm gate comprising a plurality of adjacent plane light cones each originating from one of the light sources, all of the light cones being located within the receiving angle of the projection lens. 25

5. A device for intensely illuminating a plane whose dimensions are in a ratio less than 10 to 1, comprising a plurality of linear light sources arranged parallel to each other in a row substantially transversely ofthe projection axis, means 30 associated with each lightsource to enlarge the projected light and form light spots partly overlapping in the vicinity of the plane and each covering substantially the entire plane with iight. the illumination cones of the points of the plane 35 comprising a plurality of adjacent plane light cones each originating from one of the light sources, said means comprising for each light source two cylindrical lenses arranged spaced apart in optical alignment between the light source and o plane, one of said lenses being arranged with its partly overlapping in the vicinity of the `plane and each covering substantially the entire plane with light, the illumination cones of the points of the plane comprising a plurality of adjacent 55 plane light cones each originating from 5one oi' the light sources, said means comprising for each light source a cylindrical lens arranged between the light source and plane and a cylindrical mirror arranged behind the light source, the axis of o0 the cylindrical mirror being parallel to the light -source and the axis of the lens being perpendicular to the light source. l

7. A device for intensely illuminating a plane whose dimensions are in a ratio less than 10 to l, 65 comprising a plurality of light sources arranged parallel to each other Vin a row substantially transversely the projection axis, optical means associated with each light source to enlarge the projected light and form light spots partly overlapping in' the vicinity of the plane and each covering substantially the entire plane with light, the illuminating cones of the points o! the plane consisting of a plurality of adjacent plane light cones each originating from one ot the light sources, said means comprising Vfor -eaoh nated having their edges parallel to the longitu- 'light source two cylindrical optical members ari dinal axis of the light sources arranged close toranzed in the path of the light emitted by the gether.

4 source and spaced apart with their axes perpenl dicular to each otherV and: with one axisi parallel Y JAN BERGMANS.

'to the longitudinal axis oi the light source, those CLAMOR AUGUST LAMBERTS. optical members nearer the plane to be illumi- 4 PIETER. MAR'IINUS VAN ALPHEN. 

